To cover small bleach spots, simply color them in with permanent markers of a similar color. This quick solution is generally best for short-term or emergency situations, since many markers are not colorfast and will wash out in the laundry; permanent results may require multiple treatments.
To re-dye bleached spots on a black garment, cover a flat surface with a thick layer of plastic, then spread the affected fabric evenly over it. Pour 1 tsp. of powdered black fabric dye into 1/2 cup of hot water, then stir until the crystals are fully dissolved. Dip a cotton swab into the dye solution, rub the swab gently over the bleached portions of the fabric, wait 20 to 30 minutes, then cover the fabric with a clean cloth and press it flat with a hot iron. When the fabric has cooled completely, launder the item as usual.
Should spot dyeing result in uneven coverage, it may be best to bleach the entire item and re-dye the whole thing. To do this, soak the damaged item in ordinary bleach water for 24 hours, then rinse the fabric in hydrogen peroxide to neutralize the chlorine. Once all of the color has been removed from the fabric, dye the whole thing according to the package directions. This will ensure even color distribution while eliminating unsightly bleach spots.
Excessive exposure to chlorine bleach damages cloth fibers, causing them to disintegrate. Even when the color of an item is successfully restored, fabrics that have been exposed to bleach will show obvious signs of wear and tear long before they normally would. Bleached and dyed items should be handled with care to ensure their longevity.